#!/usr/bin/env python3
"""
脚本名称：ch20_exe.py
功能描述： 演示函数和文件操作
作者：Gavin
创建日期：2022-05-06
版本：1.0
依赖库：无
使用方法： python ch20_exe.py
"""

input_file = "test.txt"


def print_all(f):
    print(f.read())


def rewind(f):
    # 移动到文件的开始
    f.seek(0)


def print_a_line(line_count, f):
    print(line_count, f.readline())


current_file = open(input_file)
print("First let's print(the whole file:\n")
print_all(current_file)

print("Now let's rewind, kind of like a tape.")
rewind(current_file)

print("Let's print(three lines:")
current_line = 1
print_a_line(current_line, current_file)

current_line = current_line + 1
print_a_line(current_line, current_file)

current_line = current_line + 1
print_a_line(current_line, current_file)
